Glass strands, for example glass fibers, rods or tubes, are typically drawn from a glass preform with a cross-sectional geometry corresponding to that of the desired final product. The production of the preform may be a continuous process in which a large hollow cylinder is either drawn into smaller tubes or it is collapsed onto a core rod in a high temperature furnace and drawn into a preform of desired diameter. The column of solid preform material is parted into sections, i.e., preforms, of a desired length from which further drawing process(es) may be used to form glass fibers, rods or tubes on a large scale.
Ideally, the parted surfaces of the preforms should be flat, smooth, perpendicular to the axis of the preform (i.e. a “square cut”), and their edges clean, sharp and free of chips or blemishes. In a continuous drawing process it is highly desirable to have a quick or instantaneous preform parting method (i.e. “snap” cut) that does not require the cutting tool to travel or move with the preform. Current “snap” cut methods of parting the solid material into preforms have been observed to create an uneven and non-perpendicular parted surfaces with chips and blemishes in the circumferential surface of the preform adjacent to the part line. Remedying the resulting surface flaws, blemishes, chips and uneven geometry results in increased production cost and decreased yield or productivity. In some cases, significant lengths of preform must be scrapped, thus reducing yield and increasing cost.
Accordingly, a need exists for a method for forming lengths of preform with improved surface characteristics and geometric precision.